When talking power production, we can’t ignore the water factor

It’s often forgotten when talking about energy production that environmental impacts stretch far beyond air pollution and emissions of heat-trapping greenhouse gases.

Less discussed, particularly in the context of electricity generation, is the dependence and impact on fresh water resources that are vital to other industries and ecosystems. If more frequent and intense droughts are to become the new normal in this era of human-induced climate change, it’s an issue that shouldn’t be overlooked by policy makers.

Don Roberts, who leads the renewable energy and clean technology investment team at CIBC, once put it this way: “If energy is scarce, water is scarcer.”

Synapse Energy Economics, a research consultancy based on Cambridge, Mass., put out a report this week drawing attention to the thirst profile and water impacts of various forms of electricity generation — namely those based on coal, natural gas, nuclear, biomass, solar and wind.

The report — called “The Hidden Costs of Electricity Generation” — also looked at climate change impacts, air pollution, subsidies, land use and development risks. For the purposes of this column the focus will be on water.

So who’s the thirstiest of them all?

It’s not wind or solar photovoltaic. The study found that only 45 to 85 gallons of water are consumed for every megawatt-hour of electricity that’s produced from a wind turbine, and that’s including the water used for manufacturing the turbine, transporting it, and constructing wind farms.

For perspective, a megawatt-hour is how much electricity the average Ontario home consumes in a month.

Solar photovoltaic electricity production doesn’t really need water, aside from negligible amounts required to occasionally clean the panels. But taking into account things like mining of photovoltaic materials and manufacturing, this type of solar generation uses six times the volume of water consumed by wind — anywhere from 225 to 520 gallons per megawatt-hour.

After wind and solar come the real water hogs — power plants that use fuels such as uranium, coal, gas and biomass to create enough heat to produce steam. The steam is then used to spin a turbine that generates electricity.

All thermal power plants need water to for cooling steam, and they need a lot. Natural gas-powered plants consume anywhere from 50 to 180 gallons per megawatt-hour depending on the approach.

Coal and biomass plants gulp 300 to 480 gallons, while nuclear plants consume up to 720 gallons for the same amount of electricity production.

(The word “consume” is used here to mean that water is used up and not returned to where it came from. Nuclear plants in Ontario, for example, withdraw tens of thousands of gallons per megawatt-hour but most goes back to the lake at a slightly higher temperature. What doesn’t is lost to evaporation.)

And remember, all of this is just cooling. The numbers rise dramatically when lifecycle costs are taken into account.

Consider that growing enough biomass — such as corn or switchgrass — to produce a megawatt-hour can consume as much as 100,000 gallons of water. Coal mining and pollution from coal plants result in widespread surface and groundwater contamination. Building and operating massive concrete structures like a nuclear plant can consume up to 6,900 gallons per megawatt-hour.

Now we’re talking big numbers. As we increasingly come to depend on shale gas to fuel our gas-fired power plants, it should be known that between two and 10 million gallons of water are required to drill and hydraulically “frack” a single shale-gas well, and that much of that water becomes contaminated with toxic chemicals.

It all adds up when one considers there are tens of thousands of shale-gas wells in some stage of development across North America.

“Such huge water withdrawals raise serious concerns about the impacts on ecosystems and drinking water supplies, especially in areas under drought conditions, areas with low seasonal flow, locations with already stressed water supplies, or locations with waters that have sensitive aquatic communities,” according to the Synapse Energy study.

The report rightly challenges the notion that low-carbon energy sources should automatically be labelled “clean” energy. It’s not just about carbon, as much as the nuclear and “clean coal” proponents would have us believe.

Water, land use, radioactivity, safety, pollution and impact on biodiversity must all be seriously weighed for their short- and long-term impacts. “What the public requires is an honest account of the true costs of electric generation technologies in as accurate a form as possible,” the study asserts.

Nuclear uses up 90 times more water than wind power. Shouldn’t that be important?

Said Grant Smith, senior energy analyst at the Civil Society Institute, the Washington, D.C.-based think tank that commissioned the Synapse study: “the government and energy industries are literally flying blind.”

3 thoughts on “When talking power production, we can’t ignore the water factor”

Tyler, for wind and solar, should that be gallons per megawatt hour produced or gallons per megawatt hour of rated power?

If we have water use embodied in the manufacture of wind and solar generation equipment the water usage per megawatt hour produced would depend on electrical production over the life of the equipment.

I find it hard to believe that a megawatt of solar panels which lasts 30 years and produces say 1000 megawatts a year, uses more water than a thermal plant that produced the same amount of electricity over whatever time span.

The second question that falls out of this is, what is the water usage embodied in the construction of the thermal plant?

I think you need to check your source for the amount of energy a typical Ontario house would use. 1 MW/H per month is an enormous amount for a residential property. Apart from that, good article. Regards